May 26, 1905.] 



SCIENCE. 



825 



A splendid series of these mounds along the 

 lower Palouse River in the vicinity o£ Winona 

 would seem, however, to point clearly to their 

 mode of origin. No feature of the Columbia 

 Basalt is more conspicuous than the isolated 

 castle-like towers and crags that persist wher- 

 ever there has been surface erosion. On the 

 ■v^alls of canyons these are especially striking. 

 One scarcely needs more than ocular evidence 

 to know that these persisting crags have re- 

 mained because formed of harder material. 

 Actual experience in blasting ditches through 

 the top of such a persisting crag demonstrated 

 it to be many times harder than ordinary 

 basalt, and of a somewhat different structure. 



In the old bed of the river near Winona the 

 series of mounds shows every gradation from 

 rock caps to mounds of basalt boulders; and 

 from these to ordinary basaltic soil. The 

 conclusion seems unavoidable, therefore, that 

 these mounds are the result of decaying basalt 

 caps, from about which flowing water had 

 previously worn the softer surrounding rock. 



The cause of these harder basalt centers 

 may be analogous to that of nodules. Be that 

 as it may, they seem to be quite evenly dis- 

 tributed through the rock, as evidenced not 

 only by their fairly regular occurrence on 

 canyon walls, but especially by the distribu- 

 tion of the mounds in old shallow stream beds. 



It was mentioned above that along canyons 

 the mounds were discernible mainly on the 

 north walls. This is due to the prevailing 

 winds of the region being southwesterly, a 

 fact that has led to the deposition of a con- 

 siderable layer of fine soil on the south walls, 

 and, therefore, the mounds are buried. The 

 occurrence of the mounds only on the crests 

 is doubtless owing to the much greater effect 

 of erosion on the slopes. 



C. Y. Piper! 



Defaetiment of Agriculture. 

 Washington, D. C. 



SPECIAL ARTICLES. 



LEVELING WITHOUT BASELEVELING. 



Since the widespread adoption of Powell's 

 views regarding baseleveling, whereby the 

 earlier views regarding marine planation 

 have been so generally displaced, truncated 



uplands — that is, uplands whose deformed 

 structure is truncated by their surface — have 

 come to be very generally interpreted as up- 

 lifted and more or less dissected peneplains. 

 Doubt has been thrown, properly enough, on 

 this interpretation in cases where the dissec- 

 tion of a supposed upland has progressed so 

 far as to transform it into a series of discon- 

 tinuous and uneven hills ; but the interpreta- 

 tion has usually and deservedly had full ac- 

 ceptance in those cases where the dissection 

 of the upland was but little advanced and 

 where the inter-valley upland areas still pre- 

 served nearly plain surfaces, whose previous 

 continuity across the valleys could not be rea- 

 sonably questioned. It is evident, however, that 

 the correctness of this interpretation depends 

 on the impossibility of the production of 

 similarly truncated uplands independent of 

 normal baselevel; and those physiographers 

 who have inferred crustal elevation on the 

 evidence of truncated uplands have doubtless 

 been convinced that this impossibility was 

 demonstrated. True, it has long been under- 

 stood that the processes of erosion and deposi- 

 tion in desert interior basins might result in 

 leveling above baselevel, the waste from the 

 highlands going to fill up the original depres- 

 sions ; but it does not appear that this process 

 has been regarded as possibly accounting, after 

 a change to a humid or normal climate and 

 without any uplift, for the occurrence of trun- 

 cated uplands in non-desert regions. 



A recent article by Dr. Siegfried Passarge, 

 of Steglitz, Germany, opens new possibilities 

 in this direction. After extended observation 

 on the desert plains of southern Africa, fully 

 described in his book, ' Die Kalahari ' (Ber- 

 lin, 190-i), Passarge concludes that these plains 

 are the result of leveling without baseleveling, 

 through the combined action of wind and water 

 erosion ; and that such plains, nearly every- 

 where showing a rock surface independent of 

 structure and interrupted only here and there 

 by residual hills or mountains — which he calls 

 by Bornhardt's term ' Insclberge ' — may be 

 produced over large areas at any altitude above 

 baselevel. His article, Rumpfflachen und 

 Inselbcrg (Zeifschr. dent. geol. Gesellsch., 

 LVL, 1904, Protokol., 193-209), in which this 



